During the last fifteen years, yellowing viruses in cucumber have become a major concern of growers due to losses in production of cucumber (Hassan: A Review of a Yellowing and Stunting disorder of Cucurbits in the United Arab Emirates Emir., J. Agric. Sci (1991), 2: 1-16). The yellowing viruses are closteroviruses. In particular, two whitefly-transmitted viruses are concerned. The viruses are known as beet pseudo-yellows virus (BPYV) which is synonymous for cucumber chlorotic spot virus and which is transmitted by Trialeurodes vaporariorum, and cucurbit yellow stunting disorder virus (CYSDV), transmitted by Bemisia tabaci. The group of closteroviruses further comprises inter alia lettuce infection yellows virus (LIYV), which is a member of the Crinivirus genus of closteroviruses. The viruses are normally retained in the vectors for approx. 7 days and are transmitted by the feeding activity of the whiteflies on the plant. Common practice of disease control is by eliminating the vectors by insecticide treatment. Until now there was no known source of resistance for the pathogens and research has been done towards elimination of the vector by insecticide treatment or by breeding for resistance towards whiteflies. Until now both approaches have been unsuccessful in controlling the diseases. It is an object of the present invention to provide cucumber plants which are resistant to closteroviruses occurring in cucumber, in particular BPSV and CYSDV.